-1- Chapter 17 Central Nervous System The spinal cord Location And External Features Internal Structure the manifestation of spinal reflex and post-trauma Functions Of The Spinal Cord Brain Nervous system
Feb 08, 2016
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Chapter 17 Central Nervous System
The spinal cord Location And External Features Internal Structure the manifestation of spinal reflex and post-trauma Functions Of The Spinal Cord
Brain
Nervous system
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shape : two enlargement : cervical enlargement⑸ lumbosacral enlargement⑹
Location And External Featuresposition : lie in vertebral canal The superior extremity is linked with medulla oblongata at the level of great occipital foramen. The inferior extremity is at the level of the inferior border of first body of lumber vertebra in adult.
Spinal cord
anterior median fissure ⑴posterior median sulcus ⑵anterolateral sulci ⑶posterolateral sulci ⑷
stripes of sulcus :
⑴ ⑵⑶
⑷
⑸
⑹
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Conus medullaris ⑴Filum terminale ⑵Cauda equina⑶ Spinal nerve ( 31 pairs )Anterior root ⑷ ( motor )Posterior root⑸ ( sense )
⑴⑵⑶
⑷⑸
⑵
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C1 - C4
C5 - T4
TIII - TVI
TVI - TIX
TX - TXII
LI
T5 - T8
T9 - T12
L1 - L5
S1 - Co1
CIV - TIII
CI - CIV - 0
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The relationship with vertebrae
vertebraespinal cord
31 segments : C8 、 T12 、 L5 、 S5 、 Co1
The spinal segment refers to a region of the spinal cord from which a pair of spinal nerves arises.
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central canal anterior (ventral) horn or anterior column posterior (dorsal) horn or posterior column lateral horn or lateral column intermediate zone central gray posterior gray commissure anterior gray commissure white matter anterior funiculus lateral funiculus posterior funiculus anterior white commissurereticular formation
terminal ventricle
Internal Structure
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Lamina ⅢLamina Ⅳ
Lamina —Ⅰ marginal layer ( areas spongiosa )Lamina —Ⅱ substantia gelatinosa
Laminas of the gray matter
Rexed layers
Lamina ⅤLamina Ⅵ
receive the afferent fibers of proprioceptive sense and regulate movement
nucleus proprius
Lamina Ⅶ
intermediomedial nucleus——is related to visceral sensory intermediolateral nucleus——is related to visceral motorthoracic nucleus ( Clark’s column )— unconscious proprioceptive sense sacral parasympathetic nucleus—is correspond to layer at the Ⅶsegment S2 - 4 , visceral motor
Lamina —Ⅷ interneuron, effect the γ and α motor neuron
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Layer — motor neuron of anterior hornⅨ medial nucleus of anterior horn : trunk muscle lateral nucleus of anterior horn : limb muscle α-motor nerve ⑴ : dominate the extrafusal muscle fiber of straddling joint→joint movement γ-motor nerve ⑵ : dominate intrafusal fiber→regulate muscular tension Renshaw cell⑶: receive α- axon collateral of motor nerve and send out branches and form reverse feedback loop with it.
layer — central grayⅩ : receive some posterior root fiber
Ⅹ⑴ ⑵
⑶
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Laminas NucleiI posteriomarginal nucleusII substantia gelatinosaIII, IV nucleus propriusV reticular nucleusVI base of posterior columnVII thoracic nucleus, intermediomedial nucleus, intermediolateral nucleus, sacral parasympathetic nucleusVIII, IX medial motor neuron column, lateral motor neuron columnX central gray matter
The relationship between the laminas and the nuclei of the spinal cord
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Tracts of the Spinal Cord
Ascending Tracts
fasciculus gracilis ⑴ below T5
fasciculus cuneatus ⑵ above T4 —conduct conscious proprioceptive sense
⑴⑵
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posterior spinocerebellar tract
anterior spinocerebellar tract —conduct unconscious proprioceptive sensespinothalamic tract lateral spinothalamic tract ⑴ —conduct crude sense of touch and pressure sensation anterior spinothalamic tract ⑵ —conduct sense of pain and warm
direct cerebellar tract
⑴
⑵
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Descending Tracts
corticospinal tract : body movement lateral corticospinal tract ⑴ anterior corticospinal tract ⑵ anterolateral corticospinal tract (of Barnes) rubrospinal tract : flexor excited vestibulospinal tract : extensor excited reticulospinal tract : motor control of proximal muscle of trunk and limbs tectospinal tract : excite the cervical muscle of opposite side, inhibit cervical muscle of homonymy medial longitudinal fasciculus : regulating the ocular movement and head position
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Functions of the Spinal Cord
Conduction pathway ;reflex centre 。spinal reflex
somatic reflexes —reflexes that result in the contraction of skeletal muscles superficial (skin and mucous membrane) reflexes and deep (myotatic) reflexes etcvisceral reflexes —the contraction of smooth or cardiac muscle or secretion by glandssuch as carotid sinus, bladder and rectal reflex,etc.
1 ) receptor , 2 ) afferent neuron , 3 ) interneurons neuron ,4 ) efferent , 5 ) effector
The simple reflex arc includes
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Stretch Reflexes
muscle 、 tendon
posterior roots
α-motor neurons
anterior roots
Muscle contraction
stretch reflex ( tendon reflexes ):
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Flexor Reflexes
skin
posterior roots
posterior horn
interneurons neuron
α-motor neurons
Muscle contraction
anterior roots
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Clinical Consideration
The spinal cord transection spinal shock Hemisection of the spinal cord Brown-Se´quard syndrome Lesion of anterior horn of the spinal cord flaccid paralysis Lesion around the central gray matter peripheral dissociation